The present invention is directed generally to reusable respiratory measurement devices which employ disposable components, and specifically to reusable spirometers having disposable flow tubes.
Respiratory measurement devices are commonly used to monitor lung performance of patients having respiratory ailments. In such applications, lung performance parameters, such as peak air flow, are periodically taken and recorded manually or electronically in a diary. If lung performance falls below a certain level or if the diary shows a deterioration in lung performance, the patient seeks medical assistance.
Such lung performance is commonly monitored using spirometry. Spirometry, the evaluation of lung function with a spirometer, is one of the simplest, most common pulmonary function tests and may be necessary for any/all of the following reasons: to determine how well the lungs receive, hold, and utilize air; to monitor a lung disease; to monitor the effectiveness of treatment; to determine the severity of a lung disease; and to determine whether the lung disease is restrictive (decreased airflow) or obstructive (disruption of airflow). As will be appreciated, a spirometer is an instrument for measuring the volume or air entering or leaving the lungs. When conducting a measurement, after taking a deep breath, a patient forcefully breathes out into the spirometer as completely and forcefully as possible. The spirometer measures and records both the amount of air expelled and how quickly the air was expelled from the lungs.
In the case of a patient who closely monitors their lung performance, it is useful to have a respiratory measurement device which is not only inexpensive and portable, but also accurate. Many inexpensive respiratory measurement devices have components which are designed to be used only once or a limited number of times. If the component is used beyond its useful life, erroneous readings may result. The erroneous readings may be the result of condensation building up within the component. This may also be due to the component being made of a relatively low-cost material which is likely to break down after a number of uses. For example, a spirometer may have a disposable component, such as a pneumotach, which typically has a fixed or variable orifice and a pressure transducer located on one or both sides of the orifice, pneumotach is a component which typically contains a pressure sensing transducer capable of measuring the amount of force exerted by the lungs in respiration. A fixed orifice is a reduced diameter passage, which can have any shape, having a fixed cross-sectional area that is independent of air flow rate. A variable orifice is a reduced diameter passage, which can have any shape, having a cross-sectional area that is dependent on air flow rate (e.g., the cross-sectional area increases as the flow rate increases). In either case, the orifice in the pneumotach may become deformed after use, resulting in erroneous measurements if the pneumotach is reused. An inaccurate measurement can cause patient misdiagnosis and/or dissatisfaction, particularly if a determination to obtain medical assistance is based on such an inaccurate measurement.
In such devices, it is necessary to replace any components which are likely to produce inaccurate readings prior to the component having significant change in condition which may reduce the accuracy of a measurement. Although directions of use can specify a components useful life, many patients often fail to read such directions and/or often reuse such components well after their useful lives, which may result in inaccurate measurements.
Additionally, such devices are often used in clinical settings, such as a hospital, clinic, or doctor""s office. In such situations, it is common for several patients to use a single portable respiratory measurement device. It is important that the mouthpiece for the device is either properly cleaned, or replaced. To provide customer convenience, portable respiratory devices commonly have disposable mouthpieces, which are replaced prior to a new patient using the device. The disposable mouthpiece helps to reduce the chances of any cross-contamination between patients using the same portable respiratory device and/or the detrimental health effects of bacteria and other microbes on the mouthpiece.
Furthermore, when disposable components are manufactured, they often have properties which are somewhat different depending upon several factors present in the manufacturing process. Thus, it is also important to have correct calibration information for such components. For example, a disposable pneumotach manufactured in a first manufacturing lot may have a slightly different orifice than a disposable pneumotach manufactured in a second manufacturing lot. Furthermore, within the same manufacturing lot, two disposable pneumotachs may have a different orifice size. These different orifice sizes must be correctly accounted for in the spirometer to ensure an accurate respiratory measurement from the spirometer. Likewise, it is important that calibration information for any such disposable component be used when determining a reading from such a device.
The present invention provides a methodology for tracking usage of disposable components, including pneumotachs or air tubes, in respiratory measurement device applications. While described with respect to respiratory applications, the invention can also be used in other applications which use non-respiratory devices that measure or detect airflow or a parameter associated therewith. A memory counter is employed to determine whether or not component usage has equaled predetermined limits and, if so, disables the respiratory measurement device. A counter is a functional unit with a number of states, each of which is associated with an incident of one or more selected events. The counter can be altered upon an appropriate signal associated with an incident of the selected event. The device can be thereafter enabled by any suitable technique, such as by replacing an old disposable memory with a new disposable memory to re-enable the respiratory measurement device, or by removing and/or attaching a selected component. In one variation, a disposable memory includes not only the counter but also calibration information.
The present invention, in its differing embodiments and configurations, can ensure that the air tubes (or devices that transport or channel airflow) are not re-used among different patients thereby reducing or eliminating cross-contamination among patients, and/or increasing the accuracy of the spirometer readings by reducing condensation buildup within the disposable air tubes and providing unique calibration information associated with a lot or batch of air tubes which can take into account performance variations among batches or lots of air tubes.
In one embodiment of the present invention, a respiratory measurement device for measuring a pulmonary condition of a patient includes:
(a) a processor operable to determine at least a first respiratory parameter based on at least a first measurement signal;
(b) a memory operable to store calibration information to determine the first respiratory parameter and a counter for tracking a number of respiratory measurements; and
(c) at least a first detachable component operable to receive a respiratory airflow of a user.
The processor and memory may be contained in a body member. The body member may be reusable. The memory can be any suitable information storage medium. For example, the memory can be one or more of ROM, PROM, EPROM, flash memory, non-volatile RAM, battery-backed-up RAM, EEPROM, a magnetic disk, and an optical disk. In one configuration, the memory module is contained in a unit that is detachable from the body member. The processor, and typically another memory module, are contained in the body member.
The first detachable component can be any suitable device for transporting or conducting a gas flow and/or measuring a parameter associated with a gas flow. By way of example, the first detachable component can be a flow tube, a pneumotach, an air tube, a respiratory filter, or mouthpiece. The first detachable component is typically an air tube. The air tube can include a sensor to provide the first measurement signal. The detachable component can measure any desirable respiratory parameter. For example, the respiratory parameter can be one or more of PEF, FEV1, FEV6, FEV1/FEV6, FVC, FEV1/FVC, and FEF25-75. In one configuration, the detachable component is disposable. Examples of detachable components include those disclosed in U.S. Pat. Nos. 5,997,483; 6,042,551; 5,564,432; 3,659,589; 5,722,417; and 5,357,972, each of which is incorporated herein by this reference.
In another embodiment, a method for monitoring use of a respiratory measurement device is provided that includes the steps of:
(a) engaging a flow tube with the respiratory measurement device;
(b) optionally engaging a monitoring unit with the respiratory measurement device, the monitoring unit including a memory including calibration information associated with at least one of the respiratory measurement device and the flow tube and a counter for determining a number of measurements taken by the respiratory measurement device;
(c) performing a respiratory measurement with the respiratory measurement device; and
(d) decrementing or incrementing the counter in response to the performing step.
The last step can be performed in a number of different ways and can be performed at a number of different times. By way of example, the counter value, in one configuration, is initially set to a permitted number of tests and is decremented by one for each test or measurement. In this configuration, the respiratory measurement device has a processor which typically determines after each test if the counter is equal to zero and, if so, disables the respiratory measurement device. In another configuration, the counter value is initially set to zero and is incremented by one for each test or measurement. In this configuration, the processor compares after each test the incremented counter to a permissible number of tests stored in the respiratory measurement device memory or in the memory of the enabling device or monitoring unit and if the permissible number of tests has the same value as the counter disables the respiratory measurement device. Step (d) can be performed after a new air tube is attached to the respiratory measurement device, when a used air tube is removed from the respiratory measurement device, immediately before, during, or after a measurement is taken, etc.
The method can include additional steps. For example, the method can further include, the steps of:
removing the monitoring unit from the respiratory measurement device;
engaging a second monitoring unit with the respiratory measurement device; and
enabling the respiratory measurement device in response to the prior step.
The last step can include the steps of reading both a second memory and a second counter in the second monitoring unit.
In another embodiment, a method for supplying a disposable flow tube for a respiratory measurement device is provided that includes the steps of:
(a) manufacturing a first plurality of disposable flow tubes for a respiratory measurement device;
(b) determining first calibration information for the first plurality of flow tubes;
(c) manufacturing a first enabling device, including a first memory storing at least one of the first calibration information and a first counter for counting a number of measurements performed by the respiratory measurement device; and
(d) packaging the first plurality of disposable flow tubes together with the corresponding first enabling device for use by a respiratory measurement device user.
Typically, the first counter is set to the number of the first plurality or batch of flow tubes. The calibration information is determined for the entire batch of flow tubes by any suitable technique. The calibration information can be based on the median performance characteristics for the batch, the average or mean performance characteristics for the batch, dimensional measurements for the batch, signal strength for one or more flow rates for the batch, or hardware used to manufacture the batch of flow tubes.
The method is typically performed on a batch-by-batch basis. For example, the method can include the further steps of:
(e) manufacturing a second plurality of disposable flow tubes;
(f) determining second calibration information for the second plurality of flow tubes;
(g) manufacturing a second enabling device, including a second memory storing the second calibration information and a second counter for counting a number of measurements performed by a respiratory measurement device attached to one of the second plurality of flow tubes; and
(h) packaging the second plurality of disposable flow tubes together with the corresponding second enabling device for use by a respiratory measurement device user.
In one configuration, the second plurality of flow tubes and second enabling device are in a different package than the first plurality of flow tubes and first enabling device. In one configuration, the first calibration information differs from the second calibration information. In one configuration, the first counter has the same value as the second counter. As will be appreciated, the flow tubes can be sold in different batch sizes so that in other configurations the first and second counters will have differing values.
The above summary is neither complete nor exhaustive. As will be appreciated, the various features noted above can be combined or separated in a variety of other embodiments and/or configurations, depending on the application. Such other embodiments and/or configurations are considered to be a part of the present invention.